Field of the Invention
The present invention relates to a polymer compound for a conductive polymer and a method for producing the same.
Description of the Related Art
A sulfo group-containing polymer is used as a fuel cell or a dopant polymer for a conductive polymer. Vinyl perfluoroalkyl ether sulfonic acid typified by Nafion (registered trademark) has been used as a material for a fuel cell, and a polymer of vinyl sulfonic acid or styrene sulfonic acid has been widely used as a dopant polymer for a conductive polymer (Patent Document 1).
Vinyl perfluoroalkyl ether sulfonic acid has high chemical stability and excellent durability, but low glass transition point. Therefore, when a fuel cell using vinyl perfluoroalkyl ether sulfonic acid is exposed to high temperature, the polymer causes thermal flow whereby ionic conductivity thereof is decreased. A superacidic polymer having a fluorinated sulfo group at the α-position is effective for an increase in ionic conductivity. However, a material having high glass transition point and high chemical stability with such a structure has not been found.
A conductive polymer having a conjugated double bond, such as polythiophene, polyaniline, and polypyrrole, does not exhibit conductivity itself. However, by doping strong acid such as sulfonic acid, the polymer exhibits conductivity. As a dopant, polystyrenesulfonic acid (PSS) is most widely used. This is because doping PSS achieves the highest conductivity.
PSS is a water-soluble resin, and is hardly dissolved in an organic solvent. Accordingly, polythiophene in which PSS is doped is also water soluble.
Since polythiophene in which PSS is doped is highly conductive and highly transparent, the polythiophene is expected as a conductive film for organic EL illumination instead of indium-tin oxide (ITO). However, a light-emitting body of organic EL causes chemical changes due to moisture and ceases to emit light. Accordingly, use of a conductive film made of a water-soluble resin for an organic EL causes a problem in which the emission lifetime of the organic EL shortens. This is because the resin contains water.